# Voltage Ampere and Temperature meter with PIC16F877A

Posted on Oct 16, 2012

This project was designed and constructed as enhancement to the 0-30V Stabilized Power Supply Project with the DIY electronics hobbyist in mind. The circuit uses a single PIC Microchip to perform the Voltage, Current and Temperature conversions and display functions. The PCB Board uses large tracks and can easily be made using the `press-n-peel` method and a hobby drill. Components should be readily available anywhere in the world. Furthermore the hex files are available for the PIC16F877A and the PIC16F887 and the display can either be LCD or LED. There is only one warning - do not attempt to construct this project unless you are sure what you are doing. Nobody else but you can make the decision to construct it and therefore you are solely responsible for what you are doing or not doing with it.

The PIC Microchip Processor must be programmed before it will function as a Volt & Amp meter. There are many internet sites and PIC programmers that you can use. I used a Microchip MPLAB ICD 2 during the project. You might need to made changes to the circuit to accommodate a different type of programmer, do read the programmers instructions carefully. The circuit relies on the internal analogue to digital converter (ADC) of the PIC Microchip Processor. The accuracy is dependant on scaling the input voltage for the ADC for all three measurements. The good news is that both the PIC's which can be used for this project have 10-Bit resolution ADC units which should work adequately in most circumstances. In order to determine the resolution, simple to advanced mathematics can be used - I will use simple mathematics and present a basic explanation in order for you to get going on the project. The Voltage of the PSU can be adjusted from 0 to 33V depending on the components in your circuit. The PIC can only measure voltages between 0 - 5V and represent the values measured as a 10bit binary number from 0 - 1024. In order to determine the voltage increments which can be measured one has to divide the scaled input voltage by 1024 and that equals: 33V/1024 = 32.2mV. Similarly the current range is 0 to 3A. Which means that we can measure in 3.0/1024 = 2.9mA increments in a near perfect circuit. Best Voltage resolution at...

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